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sem 2 > Principles of haemodynamic > Flashcards

Principles of haemodynamic Flashcards

1
Q

Define Hemodynamics?

A

Is the relationship between blood flow, blood pressure and resistance to flow

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2
Q

Define 6 terms?

A
  1. Force= Cardiac contraction
  2. Work= Isovolumetric contraction
  3. pressure= Pressure difference between aorta and veins
  4. Compliance= Stretch of the arteries
  5. Resistance= Resistant to arterioles
  6. Flow velocity= Slowing down blood flow in capillaries
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3
Q

Describe the Cardiovascular system? (4pts)

A
  1. The cardiovascular system is a closed system
  2. If we reduce blood flow to one area in the cardiovascular system it increases the pressure upstream of that area and can alter blood flow to other areas.
  3. What happens in one part of the cardiovascular system has a major impact on the other parts. Reduced blood flow to one area increases pressure upstream and alters flow to other areas.
  4. Veins are not as muscular as the arteries. They can contract slightly and when they do contract they send more blood back to the heart. According to Starlings law this will increase cardiac output as there will be more blood in so more blood out.
  5. Veins are not as muscular as the arteries. They can contract slightly and when they do contract they send more blood back to the heart. According to Starlings law this will increase cardiac output as there will be more blood in so more blood out.
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4
Q

Define Darcy Law?

A

Role of pressure energy in flow

Flow= Pressure difference/ Resistance to flow

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5
Q

Define Bernoullis law?

A

Flow= Pressure+ Kinetic V2 + Potential

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6
Q

Define Blood flow?

A

Volume of blood flowing in a given time (ml/min)

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7
Q

Define Perfusion?

A

Blood flow through a tissue ( ml/min/g)

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8
Q

Define velocity of blood flow?

A

Blood flow affected by the cross sectional area through which the blood flows so flow may remain the same but velocity changes if there has been a change in cross sectional area.

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9
Q

Describe blood flow and velocity? (4pts)

A
  1. The velocity of blood flow in the aorta is high. Branching of the arteries slows velocity
  2. The greater the cross-sectional area the slower the blood flow and the slower the blood flow in the capillaries
  3. Velocity of blood flow increases when veins come together
  4. Blood flow remains constant at 10 m/s.
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10
Q

Describe blood flow and velocity? (4pts)

A
  1. The velocity of blood flow in the aorta is high. Branching of the arteries slows velocity
  2. The greater the cross-sectional area the slower the blood flow and the slower the blood flow in the capillaries
  3. Velocity of blood flow increases when veins come together
  4. Blood flow remains constant at 10 m/s.
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11
Q

Volume flow?

A

Volume flow= Velocity x area

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12
Q

Define Laminar blood flow? (7pts)

A
  1. Laminar flow is a smooth flow
  2. The blood in the centre of the blood vessel will go faster than the blood at the edges. The blood at the edges of the blood vessel are slowed down by friction as it touches the interior wall of the vessel. This produces concentric shells
  3. 0 Velocity at the walls
  4. Maximum velocity at centre
  5. Laminar flow moves red blood cells towards the centre
  6. This speeds up blood flow through narrow vessels.
  7. Concentric shells produce low friction. This produces efficient flow
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13
Q

Describe turbulent flow? ( 3pts)

A
  1. Blood does not flow linearly and smoothly
  2. Flows in adjacent layers ( whirlpools, eddies and vortices) due to increased pressure and velocity.
  3. There is high resistance to blood flow
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14
Q

Describe Bolus flow? (3pts)

A
  1. Red blood cells have a very larger diameter than the diameter of capillaries so move in a single file
  2. Plasma columns are trapped between red blood cells
  3. Uniform velocity, little internal friction and very low resistance
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15
Q

Define Reynolds number?

A

Re= Density x velocity x diameter / viscosity

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16
Q

What happens when you increase blood pressure?

A

As you increase blood pressure you increase blood flow. At a certain point it will turn from laminar flow to turbulent flow with the formation of eddies and chaotic motion which do not contribute to the flowrate.

17
Q

When does turbulence occur?

A

when Reynolds number exceeds a critical value of 2000

18
Q

What is Poiselluiles law valid for?

A

only for conditions of laminar flow

19
Q

Describe arterial blood flow? (9pts)

A
  1. Pressure exerted by blood on the vessel walls and generated by left ventricular contraction
  2. There is a huge change in pressure in the left ventricle
  3. When the ventricles relax in diastole the pressure is very low - 80mmHg
  4. During systole pressure increases- 120 mmHg
  5. Pressure is highest in the aorta
  6. Arterial pressure falls steadily in systematic circulation with distance from the left ventricle
  7. Aorta recoils in diastole which keeps the blood flowing and prevents the pressure from falling to 0. This keeps smooth blood flow
  8. Pressure in the capillaries is very low
  9. Arterioles are the resistance vessels under sympathetic control
20
Q

Define arterial blood pressure terms?

A
  1. Systolic pressure= pressure when ejecting
  2. Diastolic pressure= pressure when relaxing
  3. Pulse pressure= difference between diastolic and systolic pressure
  4. Mean blood pressure= Average pressure
21
Q

What happens in the aorta during left ventricular systole? (2pts)

A
  1. 60-80% stroke volume is stored in the aorta and arteries as these structures expand
  2. Energy is stored in stretched elastin
22
Q

What happens in the aorta during left ventricular diastole? (2pts)

A
  1. Energy is returned to the blood as the walls of the aorta and the arteries contract
  2. This sustains diastolic pressure and blood flow when the heart is relaxed
23
Q

Define Pulse pressure?

A

Pulse pressure is what the finger senses e.g at the wrist

24
Q

Pulse pressure equation

A

Pulse pressure= Stroke volume/ Compliance

25
Q

What happens if compliance is low

A

If the compliance is low the pulse pressure will be high

26
Q

What happens when the arteries become stiff?

A

when the arteries become stiff due to factors such an ageing they will be less compliant and will have higher pulse pressures

27
Q

Define systole

A
  1. Maximum volume of blood

2. high arterial pressure of 120

28
Q

Define diastole

A
  1. Minimum volume of blood

2. Lower arterial pressure of 80

29
Q

What happens during excercise

A

During exercise there is a stronger force of contraction. there is greater stretch of arteries as more blood is ejected which causes less compliance and less recoil and the difference between systole and diastole increases which means the pulse pressure increases.

  1. Greater stroke volume
  2. Greater stretch of arteries
  3. Less compliant
  4. Greater systolic pressure
30
Q

Define compliance?

A

Change in volume/ change in pressure

31
Q

How does compliance decrease? (2 pts)

A
  1. As compliance decreases the curve goes steeper
  2. In al elderly person the aorta is stiff. If they start to exercise and increase stroke volume slightly pulse pressure will increase rapidly and there will be decreased compliance. This increases the afterload on the heart.
32
Q

What is blood pressure controlled by? (6pts)

A
  1. Age- as you get older mean blood pressure rises as the arteries get less compliant
  2. Disease- e.g cvd
  3. blood volume- a greater blood volume will give a greater blood pressure
  4. Exercise= decreases blood pressure
  5. Emotion= stress, anger, fear and pain increases blood pressure
  6. Wake/ sleep= during sleep mean blood pressure is lower

sem 2 (12 decks)

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